This investigation is designed to: 1. appraise the role of thyrotropin in the genesis, growth and progression of thyroid cancer, 2. develop isotopic and other techniques to establish better methods of distinguishing between adenomatous goiter, cysts, subacute and chronic thyroiditis and thyroid cancer, and 3. evaluate the role of suppressive therapy in the management of adenomatous goiter. Underlying these three objectives is a continuing study to characterize the biologic characteristics of the different types of thyroid cancers.